Transcriptional factor, process for producing the same and use thereof

ABSTRACT

Ascochlorin or an analog or derivative thereof and a compound having a primary amino group are mixed and reacted with each other in the presence/absence of a basic catalyst to synthesize a novel imino compound. The novel imino compound thus synthesized is a ligand capable of activating nuclear receptor superfamily such as retinoid orphan receptor (RXR), peroxisome proliferator-activated receptor (PPAR) and steroid receptor (PXR), and shows an effect of promoting the transcription of a drug-metabolizing enzyme CYP7A1. The imino compound has a therapeutic effect on diseases such as lifestyle-related diseases, chronic inflammation and cancers.

TECHNICAL FIELD

The present invention relates to novel compounds obtained from a group of microbial metabolites having a terpene side chain attached at the 3-position of orcyl aldehyde and being usually called prenylphenol antibiotics, i.e., ascochlorin, cylindrochlorin, chloronectin, LLZ-1272-•, LLZ-1272-• as well as their derivatives such as 4-O-alkyl, 2-O-alkyl, 4-O-acyl, 2-O-acyl, 2,4-diO-alkyl, 2-O-acyl-4-O-alkyl and 4-O-acyl-2-O-alkyl derivatives by reacting their aromatic aldehyde group with an amino compound (e.g., an amino acid) to synthesize their corresponding imino compounds. The present invention also relates to such a synthesis method as mentioned above. The method of the present invention is highly selective and the novel imino compounds synthesized by this method are effective in treating hypercholesterolemia, hypo-HDL-cholesterolemia, heart coronary arteriosclerosis, cerebrovascular disorders, hypertension, non-insulin-dependent diabetes mellitus, visceral fat syndrome (syndrome X), thyroid dysfunction, etc. These compounds are also effective in preventing insulin-dependent diabetes mellitus, in preventing restenosis of heart coronary arteries dilated with balloon catheters or stents, and in preventing transplanted cells, tissues and the like from being killed in regenerative medicine.

BACKGROUND ART

In 1968, Tamura, Ando and Suzuki et al. isolated novel metabolites from Hyphomycetes Ascochyta viciae Libert during screening of antiviral antibiotics and named them ascochlorin (Tamura et al. J. Antibiotics 21: 539-544, 1968). The absolute structure of ascochlorin has been determined as 3-[5-[1(R),2(S),6(S)-trimethyl-3-oxocyclohexyl]-3-methyl-2,4-pentadienyl]-2,4-dihydroxy-5-chloro-6-methylbenzaldehyde by the research group including one of the inventors (Ando) (Nawata Y. et al. J. Antibiotics 22: 1969). This substance was found to be identical to the fungus Fusarium sp. metabolite LLZ-1272-C, for which the United States Lederle Laboratories obtained a patent (U.S. Pat. No. 3,546,073, Dec. 8, 1970). Moreover, ascochlorin was found to be identical to the compound, for which Imperial Chemical Industries Ltd. (ICI) filed a patent application on Oct. 23, 1968 under GB Patent Application No. 50354/68 and filed an additional patent application on Apr. 12, 1972 in response to the structure determination of this unknown compound. However, the inventors of the present invention had already filed a Japanese patent application in March 1968 and elucidated the absolute structure of the compound in 1969 by X-ray diffraction techniques using intramolecular introduction of iodo atoms. For this reason, the designation “ascochlorin” is now accepted as a common name.

On the other hand, a carcinogenesis process in which a carcinogenic protein Ras was farnesylated in the cytoplasm and migrated to the cell membrane to cause cell canceration was among the state-of-the-art studies on cancers in late 1980s. In 1995, during screening of Ras farnesylation inhibitors among microbial metabolites, the United States Merck & Co., Inc. found that ascochlorin and its derivatives inhibited Ras farnesylation and obtained a patent for this finding (Singh, S. B et al. US Patent 94-222773 (Merck & Co., Inc., U.S.A)). Likewise, when screening inhibitors of aromatase (a rate-determining factor for androgen biosynthesis) among microbial metabolites, Ohmura et al. isolated a strong inhibitory substance out of fungal metabolites. They reported that this aromatase-inhibiting substance was cylindrochlorin when identified (Ohmura and Takamatsu et al., Chem. Pharm. Bull. 42: 953-956, 1994). All of the above compounds are common in having a structure in which a sesquiterpene side chain is attached to the 3-position of orcyl aldehyde; the inventors of the present invention collectively refer to these compounds as prenylphenol.

Prenylphenol is characterized by showing a variety of biological activities. For example, the inventors of the present invention have shown that ascochlorin arrests animal virus growth in spite of not affecting nucleic acid and protein biosynthesis. On the other hand, researchers at the Lederle Laboratories have reported that prenylphenol not only inhibits the growth of protozoan Tetrahymena, but also lowers serum cholesterol in mice and rats. In particular, they have reported that cylindrochlorin generated by dehydrogenation of the cyclohexanone ring of ascochlorin has a stronger effect of lowering serum cholesterol.

According to the above ICI's patent, ascochlorin has not only an effect of lowering serum cholesterol, but also a strong anorectic effect on rodents. This anorectic effect is strong enough to cause half inhibition of feed intake during a 2-hour intake time in mice starved for a 48-hour period receiving a trace amount of ascochlorin by oral route 2 hours before feed intake. The ICI's patent further teaches that ascochlorin has an effect of alleviating inflammatory swelling on arthritis in rats induced by adjuvant injection into their footpads.

The inventors of the present invention have isolated an ascochlorin derivative ascofuranone and have determined its structure, thus finding that this compound has a serum cholesterol-lowering effect and an anticancer effect on rodents (Jpn. J. Pharmacol. 25: 35-39, 1975 and J. Antibiotics 35: 1547-52, 1982). They have further examined pharmacological effects provided by prenylphenol, indicating that ascofuranone and 4-O-methylascochlorin prevent hypertensive rat models from entering renal failure (Eur. J. Pharmacol. 69: 429-438, 1981). Namely, prenylphenol has been found to significantly prevent hypertension which is caused in unilaterally nephrectomized rats by administering deoxycorticosterone acetate, a kind of mineral corticoid, together with 1% salt water as drinking water. It has also been found to inhibit hypercholesterolemia resulting from elevated blood pressure and to alleviate sclerotic lesions occurring in the glomeruli. Among pharmacological effects of ascochlorin derivatives, interesting are the effects of lowering serum total cholesterol in rodents and eliminating insulin resistance in non-insulin-dependent diabetes mellitus models (Agr. Biol. Chem. 46: 2865-69, 1982; DIABETES 34: 267-274, 1985).

For this reason, many studies have been carried out to synthesize novel ascochlorin derivatives using organic chemistry procedures; major articles on these studies are as shown below. The United States Lederle Laboratories have isolated ascochlorin from Fusarium fungi and synthesized several derivatives during structure determination of ascochlorin (Tetrahedron, Elstad G. A. et al: Tetrahedron 25: 1323-34, 1969). Further, Safaryn et al. (Safaryn J. E. et al.: Tetrahedron 42: 2635-42, 1986) and Mori et al. (Tetrahedron 41: 3049-62, 1985 & ibid 40: 2711-20, 1984) have succeeded in making a complete synthesis of ascochlorin. On the other hand, the above-mentioned Merck & Co., Inc. has synthesized some derivatives with the aim of obtaining a farnesyl transferase inhibitor against the carcinogenic protein Ras.

DISCLOSURE OF THE INVENTION

The inventors of the present invention have found that ascochlorin and its relevant compounds separated from natural sources as well as ascochlorin derivatives in which either or both of the 2- and 4-hydroxyl groups of orcyl aldehyde are substituted with an alkyl or acyl group(s) cause activation of nuclear receptors such as RXR (retinoid X receptor), RAR (all-trans-retinoic acid receptor) and PPAR (peroxisome proliferator-activated receptor) at the cell culture level, while they regulate the expression of gene information related to various diseases at the animal level.

Based on this finding, the inventors of the present invention have completed the present invention.

Namely, the present invention provides the inventions shown in 1 to 44 below.

-   1. A method for synthesizing a novel imino compound, which comprises     reacting an aldehyde group of a fully substituted aromatic aldehyde     compound as a filamentous fungal metabolite having a sesquiterpene     side chain at the 3-position or a derivative thereof with an amino     group of an amino compound. -   2. A method for synthesizing a novel imino compound, which comprises     reacting an aldehyde group of a fully substituted aromatic aldehyde     compound represented by the following formula as a filamentous     fungal metabolite having a sesquiterpene side chain at the     3-position or a derivative thereof:

(wherein

R₁ represents one of the following two groups:

R₃ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group, and

R₄ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group) with an amino group of an amino compound represented by the following formula: R₂NH₂ (wherein R₂ represents —(CH₂)_(n)—CHR₅R₆ (wherein R₅ represents a hydrogen atom, an amino group, an amino group substituted with one or two C₁₋₆ alkyl groups, or a C₁₋₆ alkyl group substituted with phenyl, R₆ represents a carboxyl group, —CONH₂, or —COOR₇ (wherein R₇ represents a substituted or unsubstituted C₁₋₆ alkyl group), and n represents 0 or an integer of 1 to 6) or a residue formed by removing NH₂ from any amino acid) to generate the novel imino compound of the following formula:

(wherein R₁, R₂, R₃ and R₄ are as defined above).

-   3. The method according to 1 or 2 above, wherein the fully     substituted aromatic aldehyde compound is a derivative in which the     hydrogen of the hydroxyl group at the 4-position is replaced with an     alkyl group. -   4. The method according to 1 or 2 above, wherein the fully     substituted aromatic aldehyde compound is a derivative in which the     hydrogen of the hydroxyl group at the 4-position is replaced with an     acyl group. -   5. The method according to 1 or 2 above, wherein the fully     substituted aromatic aldehyde compound is a derivative in which the     hydrogen of the hydroxyl group at the 2-position is replaced with an     alkyl group. -   6. The method according to 1 or 2 above, wherein the fully     substituted aromatic aldehyde compound is a derivative in which the     hydrogens of the hydroxyl groups at both the 2- and 4-positions are     each replaced with an alkyl group. -   7. The method according to 1 or 2 above, wherein the fully     substituted aromatic aldehyde compound is a derivative in which the     hydrogen of the hydroxyl group at the 2-position is replaced with an     alkyl group, and the hydrogen of the hydroxyl group at the     4-position is replaced with an acyl group. -   8. The method according to 1 or 2 above, wherein the fully     substituted aromatic aldehyde compound is a derivative in which the     hydrogen of the hydroxyl group at the 2-position is replaced with an     acyl group, and the hydrogen of the hydroxyl group at the 4-position     is replaced with an alkyl group. -   9. The method according to any one of 1 to 8 above, wherein the     fully substituted aromatic aldehyde compound is selected from     ascochlorin, cylindrochlorin, ascofuranone, chloronectin, LLZ-1272-•     and LLZ-1272-C•. -   10. A compound of the following formula or a pharmaceutically     acceptable salt or ester of the compound or optical isomers thereof:

(wherein

R₁ represents one of the following two groups:

R₂ represents —(CH₂)_(n)—CHR₅R₆ (wherein R₅ represents a hydrogen atom, an amino group, an amino group substituted with one or two C₁₋₆ alkyl groups, or a C₁₋₆ alkyl group substituted with phenyl, R₆ represents a carboxyl group, —CONH₂, or —COOR₇ (wherein R₇ represents a substituted or unsubstituted C₁₋₆ alkyl group), and n represents 0 or an integer of 1 to 6) or a residue formed by removing NH₂ from any amino acid,

R₃ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group, and

R₄ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group).

-   11. The compound according to 10 above, wherein R₄ is a substituted     or unsubstituted C₁₋₆ alkyl group, or a pharmaceutically acceptable     salt or ester of the compound or optical isomers thereof. -   12. The compound according to 10 above, wherein R₄ is an acyl group,     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof. -   13. The compound according to 10 above, wherein R₃ is a substituted     or unsubstituted C₁₋₆ alkyl group, or a pharmaceutically acceptable     salt or ester of the compound or optical isomers thereof. -   14. The compound according to 10 above, wherein R₃ and R₄, which may     be the same or different, are each a substituted or unsubstituted     C₁₋₆ alkyl group, or a pharmaceutically acceptable salt or ester of     the compound or optical isomers thereof. -   15. The compound according to 10 above, wherein R₃ is a substituted     or unsubstituted C₁₋₆ alkyl group and R₄ is an acyl group, or a     pharmaceutically acceptable salt or ester of the compound or optical     isomers thereof. -   16. The compound according to 10 above, wherein R₃ is an acyl group     and R₄ is a substituted or unsubstituted C₁₋₆ alkyl group, or a     pharmaceutically acceptable salt or ester of the compound or optical     isomers thereof. -   17. A pharmaceutical composition which comprises one or more members     of a compound of the following formula or a pharmaceutically     acceptable salt or ester of the compound or optical isomers thereof,     as well as a pharmaceutically acceptable additive including a     carrier and a diluent:

(wherein

R₁ represents one of the following two groups:

R₂ represents —(CH₂)_(n)—CHR₅R₆ (wherein R₅ represents a hydrogen atom, an amino group, an amino group substituted with one or two C₁₋₆ alkyl groups, or a C₁₋₆ alkyl group substituted with phenyl, R₆ represents a carboxyl group, —CONH₂, or —COOR₇ (wherein R₇ represents a substituted or unsubstituted C₁₋₆ alkyl group), and n represents 0 or an integer of 1 to 6) or a residue formed by removing NH₂ from any amino acid,

R₃ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group, and

R₄ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group).

-   18. A therapeutic or prophylactic agent for diabetes, which     comprises one or more members of the compound according to any one     of 10 to 16 above or a pharmaceutically acceptable salt or ester of     the compound or optical isomers thereof as active ingredients. -   19. A therapeutic agent for arteriosclerosis, which comprises one or     more members of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof as active ingredients. -   20. A serum cholesterol-lowering agent, which comprises one or more     members of the compound according to any one of 10 to 16 above or a     pharmaceutically acceptable salt or ester of the compound or optical     isomers thereof as active ingredients. -   21. A therapeutic agent for multiple risk factor syndrome, which     comprises one or more members of the compound according to any one     of 10 to 16 above or a pharmaceutically acceptable salt or ester of     the compound or optical isomers thereof as active ingredients. -   22. A therapeutic agent for hypertension, which comprises one or     more members of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof as active ingredients. -   23. A therapeutic agent for myxedema, which comprises one or more     members of the compound according to any one of 10 to 16 above or a     pharmaceutically acceptable salt or ester of the compound or optical     isomers thereof as active ingredients. -   24. An antiphlogistic for treating chronic inflammation, which     comprises one or more members of the compound according to any one     of 10 to 16 above or a pharmaceutically acceptable salt or ester of     the compound or optical isomers thereof as active ingredients. -   25. A prophylactic or therapeutic agent for restenosis of arterial     lumen dilated with a balloon catheter or stent, which comprises one     or more members of the compound according to any one of 10 to 16     above or a pharmaceutically acceptable salt or ester of the compound     or optical isomers thereof as active ingredients. -   26. A survival promoter for ensuring survival of cells or tissues     differentiated and induced from stem cells to be transplanted to a     recipient in regenerative medicine, which comprises one or more     members of the compound according to any one of 10 to 16 above or a     pharmaceutically acceptable salt or ester of the compound or optical     isomers thereof as active ingredients. -   27. A method for treating or preventing diabetes, which comprises     administering to a patient a therapeutically or prophylactically     effective amount of one or more members of the compound according to     any one of 10 to 16 above or a pharmaceutically acceptable salt or     ester of the compound or optical isomers thereof. -   28. A method for treating arteriosclerosis, which comprises     administering to a patient a therapeutically effective amount of one     or more members of the compound according to any one of 10 to 16     above or a pharmaceutically acceptable salt or ester of the compound     or optical isomers thereof. -   29. A method for lowering serum cholesterol, which comprises     administering to a patient a therapeutically or prophylactically     effective amount of one or more members of the compound according to     any one of 10 to 16 above or a pharmaceutically acceptable salt or     ester of the compound or optical isomers thereof. -   30. A method for treating multiple risk factor syndrome, which     comprises administering to a patient a therapeutically effective     amount of one or more members of the compound according to any one     of 10 to 16 above or a pharmaceutically acceptable salt or ester of     the compound or optical isomers thereof. -   31. A method for treating hypertension, which comprises     administering to a patient a therapeutically effective amount of one     or more members of the compound according to any one of 10 to 16     above or a pharmaceutically acceptable salt or ester of the compound     or optical isomers thereof. -   32. A method for treating myxedema, which comprises administering to     a patient a therapeutically effective amount of one or more members     of the compound according to any one of 10 to 16 above or a     pharmaceutically acceptable salt or ester of the compound or optical     isomers thereof. -   33. A method for treating chronic inflammation, which comprises     administering to a patient a therapeutically effective amount of one     or more members of the compound according to any one of 10 to 16     above or a pharmaceutically acceptable salt or ester of the compound     or optical isomers thereof. -   34. A method for preventing or treating restenosis of arterial lumen     dilated with a balloon catheter or stent, which comprises     administering to a patient a therapeutically or prophylactically     effective amount of one or more members of the compound according to     any one of 10 to 16 above or a pharmaceutically acceptable salt or     ester of the compound or optical isomers thereof. -   35. A method for ensuring survival of cells or tissues     differentiated and induced from stem cells to be transplanted to a     recipient in regenerative medicine, which comprises administering to     a recipient an effective amount of one or more members of the     compound according to any one of 10 to 16 above or a     pharmaceutically acceptable salt or ester of the compound or optical     isomers thereof. -   36. The use of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof for the manufacture of a therapeutic or     prophylactic agent for diabetes. -   37. The use of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof for the manufacture of a therapeutic agent     for arteriosclerosis. -   38. The use of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof for the manufacture of a serum     cholesterol-lowering agent. -   39. The use of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof for the manufacture of a therapeutic agent     for multiple risk factor syndrome. -   40. The use of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof for the manufacture of a therapeutic agent     for hypertension. -   41. The use of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof for the manufacture of a therapeutic agent     for myxedema. -   42. The use of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof for the manufacture of an antiphlogistic for     treating chronic inflammation. -   43. The use of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof for the manufacture of a prophylactic or     therapeutic agent for restenosis of arterial lumen dilated with a     balloon catheter or stent. -   44. The use of the compound according to any one of 10 to 16 above     or a pharmaceutically acceptable salt or ester of the compound or     optical isomers thereof for the manufacture of a survival promoter     for ensuring survival of cells or tissues differentiated and induced     from stem cells to be transplanted to a recipient in regenerative     medicine.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of the mechanism whereby target cells are affected by an ascochlorin-lysine Schiff base formed in the small intestinal lumen from lysine and an ascochlorin derivative attached to feed protein.

FIG. 2 is a graph illustrating the relationship between duration and blood active substance level for each case of first-, second- and third-generation drugs.

BEST MODE FOR CARRYING OUT THE INVENTION

As used herein, the phrase “fully substituted aromatic aldehyde compound as a filamentous fungal metabolite having a sesquiterpene side chain at the 3-position or a derivative thereof” is intended to mean a compound of the following formula:

(wherein

R₁ represents one of the following two groups:

R₃ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group, and

R₄ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group).

The numbering of carbon atoms on the benzene ring is made as follows: the 1-position is given to the carbon atom attached to the aldehyde group, followed by the 2-, 3- to 6-positions in a clockwise direction.

As used herein, the term “C₁₋₆ alkyl group” means a linear or branched C₁₋₆ alkyl group. Examples of a C₁₋₆ alkyl group include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl and n-hexyl. Such a “C₁₋₆ alkyl group” may have one or more substituents selected from, for example, hydroxy, amino, carboxyl, nitro, an aryl group, a substituted aryl group, mono- or lower alkylamino (e.g., mono- or di-C₁₋₆ alkylamino such as methylamino, ethylamino, propylamino, dimethylamino or diethylamino), alkoxy (e.g., C₁₋₆ alkoxy such as methoxy, ethoxy, propoxy or hexyloxy), alkylcarbonyloxy (e.g., C₁₋₆ alkyl-carbonyloxy such as acetoxy or ethylcarbonyloxy) or a halogen atom.

As used herein, the term “C₂₋₆ alkenyl group” means a linear or branched C₂₋₆ alkenyl group. Examples of a C₂₋₆ alkenyl group available for use include vinyl, allyl, 2-methylallyl, i-propenyl, 2-butenyl, 3-butenyl, 2-pentenyl, 3-pentenyl, 2-hexenyl and 3-hexenyl. Such a “C₂₋₆ alkenyl group” may have one or more substituents selected from, for example, hydroxy, amino, carboxyl, nitro, mono- or di-alkylamino (e.g., mono- or di-C₁₋₆ alkylamino such as methylamino, ethylamino, propylamino, dimethylamino or diethylamino), alkoxy (e.g., C₁₋₆ alkoxy such as methoxy, ethoxy, propoxy or hexyloxy), alkylcarbonyloxy (e.g., C₁₋₆ alkyl-carbonyloxy such as acetoxy or ethylcarbonyloxy) or a halogen atom.

As used herein, the term “C₂₋₆ alkynyl group” means, for example, a linear or branched C₂₋₆ alkynyl group. Examples of a C₂₋₆ alkynyl group available for use include ethynyl, 2-propynyl, 2-butynyl, 3-butynyl, 2-pentynyl, 3-pentynyl, 2-hexynyl and 3-hexynyl. Such a “C₂₋₆ alkynyl group” may have one or more substituents selected from, for example, hydroxy, amino, carboxyl, nitro, mono- or di-alkylamino (e.g., mono- or di-C₁₋₆ alkylamino such as methylamino, ethylamino, propylamino, dimethylamino or diethylamino), alkoxy (e.g., C₁₋₆ alkoxy such as methoxy, ethoxy, propoxy or hexyloxy), alkylcarbonyloxy (e.g., C₁₋₆ alkyl-carbonyloxy such as acetoxy or ethylcarbonyloxy) or a halogen atom.

As used herein, the term “C₃₋₈ cycloalkyl group” is intended as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, cyclooctyl group, etc. Such a “cycloalkyl group” may have one or more substituents selected from, for example, hydroxy, amino, carboxyl, nitro, mono- or di-alkylamino (e.g., mono- or di-C₁₋₆ alkylamino such as methylamino, ethylamino, propylamino, dimethylamino or diethylamino), alkoxy (e.g., C₁₋₆ alkoxy such as methoxy, ethoxy, propoxy or hexyloxy), alkylcarbonyloxy (e.g., C₁₋₆ alkyl-carbonyloxy such as acetoxy or ethylcarbonyloxy) or a halogen atom.

In a case where R₂ represents a residue formed by removing NH₂ from any amino acid, examples of any amino acid intended herein include lysine, hydroxylysine, arginine, glycine, alanine, valine, leucine, isoleucine, serine, threonine, aspartic acid, glutamic acid, asparagine, glutamine, cysteine, cystine, methionine, phenylalanine, tyrosine, tryptophan, histidine, proline, β-alanine, γ-aminobutyric acid, homocysteine, ornithine, 5-hydroxytryptophan, 3,4-dihydroxyphenylalanine, triiodothyronine and thyroxine.

As used herein, the term “acyl group” means a group represented by —COR (wherein R represents any one of a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, and a monocyclic or polycyclic aromatic or heterocyclic ring). Such an “acyl group” and an “acylamino group” may each have one or more substituents selected from, for example, hydroxy, amino, carboxyl, nitro, mono- or di-alkylamino (e.g., mono- or di-C₁₋₆ alkylamino such as methylamino, ethylamino, propylamino, dimethylamino or diethylamino), alkoxy (e.g., C₁₋₆ alkoxy such as methoxy, ethoxy, propoxy or hexyloxy), alkylcarbonyloxy (e.g., C₁₋₆ alkyl-carbonyloxy such as acetoxy or ethylcarbonyloxy) or a halogen atom; and such a substituent means a substituent located on R.

As used herein, the term “aryl group” means an atomic group left by removing one hydrogen atom from an aromatic hydrocarbon. Particularly preferred is a C₆₋₁₄ aryl group. Examples of a C₆₋₁₄ aryl group available for use include phenyl, naphthyl, tolyl, xylyl, biphenyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, 9-phenanthryl, 1-azulenyl, 2-azulenyl, 4-azulenyl, 5-azulenyl and 6-azulenyl. Such an “aromatic ring” may have one or more substituents selected from, for example, lower alkyl, hydroxy, amino, carboxyl, nitro, mono- or di-lower alkylamino (e.g., mono- or di-C₁₋₆ alkylamino such as methylamino, ethylamino, propylamino, dimethylamino or diethylamino), lower alkoxy (e.g., C₁₋₆ alkoxy such as methoxy, ethoxy, propoxy or hexyloxy), lower alkylcarbonyloxy (e.g., C₁₋₆ alkyl-carbonyloxy such as acetoxy or ethylcarbonyloxy), trihalomethane, trihalomethoxy, a halogen atom or aryl such as phenyl.

As intended herein, a particularly preferred salt is a pharmaceutically acceptable acid addition salt. Examples of such a salt available for use include those with inorganic acids (e.g., hydrochloric acid, phosphoric acid, hydrobromic acid, sulfuric acid), those with organic acids (e.g., acetic acid, formic acid, propionic acid, fumaric acid, maleic acid, succinic acid, tartaric acid, lactic acid, citric acid, malic acid, oxalic acid, benzoic acid, methanesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid) or those with alkalis (e.g., sodium, potassium, magnesium, calcium, ammonium, pyridine, triethylamine).

As intended herein, a particularly preferred ester is an alkyl ester (e.g., methyl ester, ethyl ester, n-propyl ester, i-propyl ester) of a carboxyl group, if any.

The Schiff base (imino compound) of the present invention also encompasses all stereoisomers and optical isomers.

Ascochlorin and 4-O-methylascochlorin having a methylated hydroxyl group at the 4-position (Compound-1) are both fat-soluble and substantially insoluble in water. Since single molecules of these compounds are released and dissolved at a very slow rate from their crystal lattices into water, most of them pass through the digestive tract without being absorbed when orally administered to small animals (e.g., rats, mice) in the fasting state. In addition to low bioavailability, their effectiveness will be affected by the presence or absence of dietary intake (Agr. Biol. Chem. 46: 775-781, 1982). Poor reproducibility in animal experiments has constituted a serious obstacle to the practical use of these compounds.

The rate of releasing and dissolving single molecules from crystal lattices into water can be increased by intramolecular introduction of a polar group. In fact, 4-O-carboxymethylascochlorin (Compound-2) derived from ascochlorin by replacing the hydrogen of the hydroxyl group at the 4-position with —CH₂COOH can be dissolved in water in an amount of 6% or more in the small intestine (pH 7.2 to 7.4); this derivative will be rapidly absorbed and hence is likely to show toxicity when orally administered.

TABLE 1 Comparison on activity between in-feed administration and forced oral administration Compound Spraying of acetone solution Mechanical mixing Forced oral administration Decrease in serum 1 15.2%-25.1% decrease, P < 0.01 No decrease in all three tests No decrease in all three cholesterol levels in all three tests Serum is not colored. tests Serum is not colored. (n = 6), tested in Serum is vivid yellow. triplicate 2 17.5%-22.7% decrease, P < 0.01 14.8%, P < 0.05 4.8%, ns in all three tests 8.2%, ns 10.9%, ns Serum is yellow. 7.2%, ns 8.8%, ns % Reduction of urinary 1 Urinary sugar excretion is No inhibitory effect is observed No inhibitory effect is sugar excretion reduced; 98.5%, 97.3% and against urinary sugar excretion observed against urinary (n = 4), tested in 99.0%, P < 0.01 in all three tests in all three tests sugar excretion in all triplicate three tests 2 Urinary sugar excretion is Urinary sugar excretion is Toxic death; reduced; 99.2%, 97.6% and reduced; 52.1%, P < 0.05, 38.5% 2/4 in the first test 98.0%, P < 0.01 in all three tests (ns) and 41.8% P < 0.05 1/4 in the second test Feed intake is reduced and 1/4 in the third test body weight gain is inhibited. Not effective Note 1) All data were analyzed by Student's paired t-test using a drug-untreated group as a control. Note 2) Effect on serum total cholesterol: Male ICR mice (5 weeks of age) were administered with a drug for 1 week, followed by blood collection from the heart to determine the level of serum cholesterol for each mouse by the Zurkowski method. Note 3) Urinary sugar excretion: db/db mice (6-7 weeks of age, male 2, female 2) were housed in a rat cage for urine collection and administered with a drug. Urine was collected every day, and the amount of urine and the concentration of urinary sugar were measured to calculate the level of urinary sugar excretion per animal.

In contrast, the solubility of Compound-1 in water is as extremely low as about 0.7 g/l; Compounds-1 and -2 are poles apart in terms of solubility in water. Interestingly, when dissolved in acetone and sprayed over feed in an amount of 0.1% for uniform penetration before being given to mice, both ascochlorin derivatives exert substantially equal effects in lowering serum total cholesterol (in normal mice) and inhibiting urinary sugar excretion (in genetically obese diabetic mice, C57BL/ksj db/db) (Table 1). However, even when both compounds are simply mixed in a mechanical manner into feed in an amount of 0.1% or even when both compounds are given for forced oral administration in the same drug amount calculated from feed intake, there is no reproducibility in their efficacy unlike the case where their acetone solutions are sprayed over feed. In particular, the water-insoluble Compound-1 shows little efficacy unless it is dissolved in acetone and sprayed over feed.

The fact that in spite of such a large difference in water solubility, both compounds show substantially equal pharmacological effects when dissolved in acetone, sprayed over feed and air-dried before being given to animals suggests the presence of some interaction between drug and feed. Then, an attempt was made to collect each compound from feed sprayed with the drug dissolved in acetone or feed prepared by mechanical mixing with each drug powder. Each feed was allowed to stand overnight at room temperature and then extracted with 20 volumes of acetone to collect each compound (Table 2).

TABLE 2 Collection experiment of Compounds-1 and -2 dissolved in acetone and sprayed over feed Feed sprayed with acetone solution Feed prepared by mechanical mixing (air-dried) with drug Extraction Recovery Extraction Extraction Recovery time rate (%) solvent time rate (%) Com- 1 hour  0 Com- 1 hour  86 pound-1 6 hours 0 pound-1 6 hours 90 16 hours  0 16 hours  85 Com- 1 hour  0 Com- 1 hour  91 pound-2 6 hours 0 pound-2 6 hours 90 16 hours  0 16 hours  76 Compounds-1 and -2 in the extracts were quantified by HPLC. Extraction conditions: room temperature

As shown in Table 2, in a case where both compounds are respectively dissolved in acetone, sprayed over feed and then air-dried, they are not extracted at all even after being immersed and extracted in acetone for 16 hours. However, in a case where both compounds are respectively mixed in a mechanical manner into feed powder, they are extracted, upon addition of acetone, into the solvent independently of the extraction time. This fact suggests that when acetone solutions of both compounds are sprayed over feed powder, these compounds cause chemical reaction with some component in the feed to form covalent bonding.

Next, feed powder which had been sprayed with an acetone solution of each compound and then air-dried was added to an organic solvent supplemented with an acid (e.g., acetic acid, hydrochloric acid) and sampled over time to quantify each compound released into the solvent. As shown in Table 3, when each feed was immersed in the acidic organic solvent, the amount of each compound released from the feed was increased with the passage of time. This fact means that Compounds-1 and -2, when dissolved in acetone and sprayed over feed, form covalent bonds with a feed component(s) simultaneously with evaporation of acetone, while such covalent bonds are hydrolyzed upon addition of an acid. This reaction is an extremely rare reaction occurring between solid phase and liquid layer. As a similar reaction, the “aminocarbonyl reaction” can be presented which is observed in foods containing a mixture of proteins and reducing carbohydrates. However, such a reaction between protein and reducing carbohydrate proceeds in an irreversible manner and finally provides a brown substance, whereas the reaction between prenylphenol and feed protein is characterized by its reversibility.

TABLE 3 Release of both compounds from feed in acidic organic solvent Recovery rate (%) Com- 0 1 8 16 Acidic organic solvent pound hours hour hours hours 5% Acetic acid- Com- 10.2 33.9 65.0 81.7 containing ethanol pound-1 Com- 8.6 41.3 71.3 79.5 pound-2 5% Hydrochloric acid- Com- 40.0 80.4 92.1 97.4 containing methanol pound-1 Com- 53.2 84.2 99.6 100.4 pound-2 Compounds-1 and -2 in the extracts were quantified by HPLC and compared with their initial amounts to calculate the recovery rate.

Ascochlorin compounds are characterized by having an aromatic aldehyde group and a 6-membered cyclic ketone side chain. They all have the possibility of forming an imino compound with the ω-amino group of a protein lysine residue. Then, glycine ethyl ester and glycine amide were selected as model compounds and mixed with ascochlorin, ascofuranone, Compound-1 or Compound-2 in an organic solvent in the presence of triethanolamine. Upon mixing, each solution immediately turned yellow, which was indicative of the formation of a new compound. When the reaction solutions were developed on silica gel thin-layer chromatography, the spots corresponding to ascochlorin, ascofuranone, Compound-1 and Compound-2 were found to disappear and instead new yellow spots were found to appear. Moreover, when the reaction solutions were concentrated and applied to silica gel column chromatography, yellow substances could be isolated in pure form. Ascochlorin and Compound-1 are fat-soluble and easily dissolved in chloroform, ethyl acetate or the like, but are difficult to dissolve in methanol. In contrast, the yellow substances formed upon mixing with glycine ethyl ester or glycine amide are insoluble in a low polar solvent such as chloroform or benzene, but are soluble in methanol. They can also be dissolved in water to some extent although their original compounds are not dissolved in water at all. In a case where an ascochlorin or ascofuranone compound is used as prenylphenol for use in producing the compound of the present invention, the following compounds can be presented as examples.

The structures of yellow substances formed by reaction between prenylphenols and primary amino compounds were elucidated by infrared absorption spectra and NMR spectra. When analyzing the NMR spectra, the proton of aldehyde was found to disappear and instead an amino proton was found to appear. The infrared absorption spectra proved that a primary amino compound is attached to the aldehyde group, but not to ketone in the cyclohexanone ring because the carbonyl absorption band of the aldehyde group disappeared simultaneously with the appearance of a stretching vibration band of —C═H—. Namely, prenylphenol and glycine amide are reacted as shown in [Reaction Scheme 1] below and, moreover, this reaction is reversible.

As long as it has a primary amino group, any compound can achieve the above reaction without exceptions. In particular, protein-constituting amino acids are preferred as materials for synthesis of imino compounds. It is certainly an imino compound-forming reaction that occurs when prenylphenol is dissolved in acetone and sprayed over feed. Feed proteins covalently attached to prenylphenol will be hydrolyzed in the small intestine by the action of proteases. Finally, a lysine residue having prenylphenol attached at the ω-position or an oligopeptide containing such a lysine residue will be readily absorbed from the digestive tract because of its increased dissolution rate in water when compared to ascochlorin or Compound-1.

In contrast, a rapidly absorbable prenylphenol like Compound-2 is covalently attached to the ω-amino group of a protein lysine residue and, as a result of feed protein hydrolysis, produces a lysine residue having prenylphenol attached at the ω-position or an oligopeptide containing such a lysine residue, thus slowing its absorption into the small intestine. In this case, Compound-2 is therefore prevented from being absorbed at once and in a large amount compared to simple administration of Compound-2, so that toxicity is less likely to occur. Although the effect of Compound-2 is time-dependent, Compound-2 will continue to be maintained at an effective blood level, which leads to increased efficacy. The interaction between ascochlorin or its derivative and feed protein is as shown in FIG. 1.

An example will be given below to illustrate how to synthesize the Schiff base (imino compound) of the present invention.

1. Ascochlorin Compounds for Use as Starting Materials

As starting materials for synthesis of ascochlorin derivatives, the above-listed ascochlorin (AC), 4-O-methylascochlorin (MAC), 4-carboxymethylascochlorin (AS-6) and ascofuranone (AF) were used.

2. Synthesis of Acetylascochlorin Compounds

<Synthesis>

The ascochlorin compounds (AC, MAC, AS-6, AF) were acylated with acetic anhydride/pyridine, extracted with ethyl acetate, washed with diluted hydrochloric acid and saturated aqueous sodium bicarbonate, and then concentrated to give crude acetylascochlorin compounds.

The 2-O-, 4-O-diacetyl form was further partially hydrolyzed in triethylamine/aqueous THF to give a 4-O-monoacetyl form. The resulting acetylascochlorin compounds are shown below.

<Acetylascochlorin Compounds>

No. Abbreviation Structural formula 22 diAcAC

34 AcAC

36,37 AcAC

43 AcMAC

45 diAcAF

<TLC, IR, NMR>

TLC (thin-layer chromatography), IR and NMR data of the above acetylascochlorin compounds are summarized in the tables shown later.

3. Synthesis of Schiff Bases of Acetylascochlorin Compounds

<Synthesis>

The ascochlorin compounds (starting materials) or the acetylascochlorin compounds prepared above were condensed with amino acid derivatives having a primary amine in the presence or absence of a base (e.g., triethylamine, potassium carbonate) and in a solvent (e.g., methanol, THF).

After confirming the progress of condensation (i.e., the appearance of band yellow spots as a result of the formation of Schiff bases) by TLC, the Schiff bases were extracted from the reaction solutions and then evaporated to remove the solvent, or alternatively, the reaction solvent was directly distilled off under reduced pressure. In this way, concentrates containing the Schiff bases were obtained.

After concentration, silica gel column chromatography was performed to isolate the Schiff bases.

As shown in the list below, each Schiff base had a structure concentrated between the salicylaldehyde site and the primary amine.

<Schiff Bases of AC>

No. Abbreviation R 5,7 AC + LysOH

6,8 AC + GlyOMe

9 AC + GlyOH

13 AC + GlyNH₂

16 AC + NAcLysOH

31 AC + âAlaNH₂

41 AC + PheNH₂

AC (Ascochlorin, R: ═O) <Schiff Bases of MAC>

No. Abbreviation R 17 AS-6 + GlyNH₂

18 AS-6 + GlyOMe

19 AS-6 + NAcLysOH

30 AS-6 + âAlaNH₂

28 MAC + Orn

40 MAC + PheNH₂

42 MAC + AlaNH₂

AS-6(4-O-Carboxymethylascochlorin, R: ═O) <Schiff Bases of AS-6> <Schiff Bases of AF>

No. Abbreviation R 15 AF + GlyNH₂

AF(Ascofuranon, R: ═O) <Schiff Bases of AcAC>

No. Abbreviation R 23 AcAC + GlyNH₂

26 AcAC + GlyOMe

27 AcAC + âAlaNH₂

37 AcAC + âAlaNH₂

39 AcAC + PheNH₂

44 AcAC + AlaNH₂

AcAC (Acetylascochlorin, R: ═O) <Schiff Bases of AcAF>

No. Abbreviation R 48 AcAF + AlaNH₂

AcAF(Acetylascofuranon, R: ═O) <TLC, IR, NMR>

TLC, IR and NMR data of the above acetylascochlorin compounds are summarized in the tables shown later.

4. Synthesis of Acetals of Ascochlorin Compounds

<Synthesis>

2-O-Acetylascochlorin compounds are condensed with alcohols in the presence or absence of a reaction solvent by the action of a base catalyst.

After confirming the progress of the reaction by TLC, the reaction solutions were evaporated to remove the reaction solvent and then crystallized, or alternatively, the concentrates of the reaction solutions were applied to silica gel column chromatography, thereby obtaining acetals.

<Acetals of Ascochlorin Compounds>

No. Abbreviation R 32 diMeAcAC

35 diEtAcAC

46 diEtMAC

47 diEtAcAF

49 diBuMAC

50 PGMAC

5. Silica Gel TLC Data of Ascochlorin Derivatives

To confirm the Rf values and purity of various ascochlorin derivatives, TLC analysis was performed. The results obtained are shown below.

No. AC compound & Schiff base Developing solvent Rf value TLC purity  6, 8 AC GlyOMe 50% AcOEt/Hexane 0.33 One spot 10 MAC GlyOMe 50% AcOEt/Hexane 0.36 One spot 11 MAC GlyNH₂  5% MeOH/CHCl₃ 0.53 Slightly impure 13 AC GlyNH₂  5% MeOH/CHCl₃ 0.57 One spot 14 MAC NAcLysOH 20% MeOH/CHCl₃ 0.04 Impure (decomposed?) 15 AF GlyNH₂ 10% MeOH/CHCl₃ 0.54 One spot 16 AC NAcLysOH 20% MeOH/CHCl₃ 0.27 One spot 17 AS-6 GlyNH₂ 20% MeOH/CHCl₃ 0.41 One spot (containing Et₃N) 18 AS-6 GlyOMe 20% MeOH/CHCl₃ 0.57 One spot 22 diAcAC 30% AcOEt/Hexane 0.33 Spot slightly above 23 AcAC GlyNH₂ 10% MeOH/CHCl₃ 0.48 Spot slightly above 25 MAC âAlaNH₂ 10% MeOH/CHCl₃ 0.42 One spot 26 AcAC GlyOMe 30% AcOEt/Hexane 0.22 Spot slightly above 27 AcAC âAlaNH₂ 10% MeOH/CHCl₃ 0.42 One spot 30 AS-6 âAlaNH₂ 30% MeOH/CHCl₃ 0.58 One spot 31 AC âAlaNH₂ 10% MeOH/CHCl₃ 0.49 One spot 32 diMeAcAC 30% AcOEt/Hexane 0.38 One spot 34 AcAC 30% AcOEt/Hexane 0.46 Substantially one spot 35 diEtAcAC 30% AcOEt/Hexane 0.48 One spot 36 AcAC 30% AcOEt/Hexane 0.46 One spot (crystalline) 37 AcAC âAlaNH₂ 10% MeOH/CHCl₃ 0.42 Alternative to No. 27. Same Rf 39 AcAC PheNH₂ 10% MeOH/CHCl₃ 0.39 Substantially one spot 40 MAC PheNH₂ 10% MeOH/CHCl₃ 0.36 Substantially one spot 41 AC PheNH₂ 10% MeOH/CHCl₃ 0.28 Substantially one spot 42 MAC AlaNH₂ 10% MeOH/CHCl₃ 0.53 One spot 43 AcMAC 30% AcOEt/Hexane 0.40 Substantially one spot 44 AcAC AlaNH₂ 10% MeOH/CHCl₃ 0.62 One spot 45 diAcAF 30% AcOEt/Hexane 0.42 Substantially one spot 46 diEtMAC 30% AcOEt/Hexane 0.58 One spot (crystallized) 47 diEtAcAF 20% AcOEt/Hexane 0.33 One spot 48 AcAF AlaNH₂ 10% MeOH/CHCl₃ 0.58 One spot 49 diBuMAC 20% AcOEt/Hexane 0.45 One spot 50 PGMAC 30% AcOEt/Hexane 0.31 One spot 6. IR Data of Ascochlorin Derivatives

To confirm the structures of various ascochlorin derivatives, IR measurement was performed. The results obtained are shown below.

Starting AC

Starting No. AC cm⁻¹ AC 3384, 2690, 2926, 2875, 1704, 1629, 1457, 1423, 1374, 1284, ------ MAC 3422, 2966, 1715, 1641, 1600, 1449, 1399, 1355, 1286, 1269, 1249, 1229, 1108, 1003, 972, 790 AS-6 3447, 2938, 1738, 1712, 1638, 1456, 1431, 1407, 1364, 1308, 1249, 1228, 1121, 967, 955, 792, 727, 638 AF 3367, 2974, 2928, 1739, 1633, 1420, 1283, 1246, 1110, 822, 593 AcAC

No. AcAC cm⁻¹ 22 diAcAC 2973, 2874, 1779, 1703, 1450, 1369, 1299, 1256, 1169, 1082 34 AcAC 2973, 1779, 1711, 1642, 1411, 1372, 1294, 1246, 1193, 1093, 1008, 970 36, 37 AcAC 3423, 2970, 1774, 1712, 1642, 1375, 1292, 1248, 1192, 1092 43 AcMAC 2974, 2873, 1774, 1700, 1585, 1369, 1307, 1176, 1095, 970, 755 45 diAcAF 2978, 1755, 1699, 1589, 1560, 1369, 1300, 1187, 1078, 1000, 878, 755 AC Schiff Base

No. AC Schiff base cm⁻¹  6, 8 AC + GlyOMe 3418, 2971, 1739, 1709, 1622, 1437, 1254, 1208, 1180, 1111, 969 13 AC + GlyNH₂ 3439, 2974, 1698, 1666, 1606, 1419, 1252, 1109, 969 16 AC + NAcLysOH 3420, 3385, 2931, 1705, 1634, 1252, 1111, 1016, 970, 908, 755 31 AC + aAlaNH₂ 3161, 2972, 1677, 1627, 1541, 1445, 1252, 1112, 969, 756 41 AC + PheNH₂ 3422, 2956, 1710, 1623, 1543, 1437, 1375, 1254, 1171, 1110, 1013, 970 MAC Schiff base

No. MAC Schiff base cm⁻¹ 10 MAC + GlyOMe 3445, 2972, 1749, 1710, 1625, 1417, 1252, 1203, 1108, 1016, 970 11 MAC + GlyNH₂ 3423, 2972, 2936, 1702, 1620, 1414, 1251, 1109, 1012, 970 14 MAC + NAcLysOH 3384, 3418, 2934, 1704, 1633, 1421, 1249, 1116, 1020, 730 25 MAC + âAIaNH₂ 2971, 1673, 1623, 1416, 1250, 1109, 1012 40 MAC + PheNH₂ 3446, 2936, 1711, 1621, 1454, 1414, 1358, 1250, 1167, 1108, 1003, 970, 751, 698 42 MAC + AlaNH₂ 3346, 3190, 2974, 2936, 2873, 1702, 1615, 1452, 1414, 1374, 1251, 1109, 970, 756 AS-6 Schiff Base

No. AS-6 Schiff base cm⁻¹ 17 AS-6 + GlyNH₂ 3419, 2977, 2939, 2677, 2605, 2497, 1702, 1618, 1475, 1398, 1316, 1252, 1114, 1037 18 AS-6 + GlyOMe 3447, 2956, 1748, 1708, 1623, 1419, 1252, 1205, 1112 19 AS-6 + NAcLysOH 30 AS-6 + âAlaNH₂ 3407, 2974, 1672, 1622, 1418, 1250, 1115, 1018, 750 AF Schiff Base

No. AF Schiff base cm⁻¹ 15 AF + GlyNH₂ 3445, 3360, 2974, 2921, 1750, 1682, 1646, 1601, 1434, 1373, 1308, 1254, 1165, 1113, 977, 607 AcAC Schiff Base

No. AcAC Schiff base cm⁻¹ 23 AcAC + GlyNH₂ 3346, 2971, 2873, 1777, 1703, 1626, 1422, 1370, 1291, 1250, 1200, 1095 26 AcAC + GlyOMe 2957, 1753, 1709, 1628, 1424, 1372, 1251, 1200, 1097, 1014 27 AcAC + âAlaNH₂ 3425, 2972, 1776, 1674, 1628, 1423, 1371, 1200, 1095 39 AcAC + PheNH₂ 3442, 2971, 1777, 1736, 1711, 1626, 1454, 1421, 1371, 1249, 1198, 1096, 1010, 970 44 AcAC + AlaNH₂ 3734, 2974, 1777, 1704, 1621, 1421, 1371, 1250, 1200, 1089, 970, 788 AcAF Schiff Base

No. AcAF Schiff base cm⁻¹ 48 AcAF + AlaNH₂ 3195, 2978, 2929, 1754, 1686, 1621, 1421, 1372, 1249, 1195, 1173, 1113 Acetal of AC

No. Acetal of AC cm⁻¹ 32 diMeAcAC 3290, 2972, 1778, 1711, 1415, 1371, 1231, 1200, 1108, 1055, 968 35 diEtAcAC 3264, 2975, 1778, 1712, 1414, 1371, 1327, 1231, 1200, 1101, 1048, 1003 46 diEtMAC 3289, 2977, 2933, 1703, 1608, 1575, 1449, 1408, 1388, 1373, 1326, 1108, 1069, 1053, 979 47 diEtAcAF 2978, 1752, 1638, 1373, 1196, 1050, 998, 752, 664 49 diBuMAC 3303, 2959, 2872, 1712, 1605, 1571, 1454, 1405, 1328, 1227, 1107, 970 50 PGMAC 3315, 2972, 2870, 1710, 1573, 1456, 1396, 1331, 1238, 1110, 987 7. NMR Data of Ascochlorin Derivatives

To confirm the structures of various ascochlorin derivatives, IR measurement was performed. The results obtained are shown below.

-   1) The structure of each acetylascochlorin compound was confirmed by     disappearance of the hydrogen of the phenolic hydroxyl group and     appearance of hydrogens of an acetoxy group as a result of     acetylation. -   2) The structure of each Schiff base was confirmed by disappearance     of the aldehyde hydrogen, appearance of an azomethine hydrogen, and     appearance of hydrogen(s) belonging to the attached amino acid     derivative. -   3) The structure of an acetal of each AC compound was confirmed by     disappearance of the aldehyde hydrogen, detection of a dioxymethine     hydrogen, and detection of hydrogen(s) belonging to the attached     alcohol.

No. Starting AC 2-OH Ar—CHO 4-OH  1 AC 12.68 10.12 6.37  1 MAC 12.51 10.23 17 AS-6 10.26 10.26 15 AF 12.67 10.12 6.43 unit: ppm

No. AcAC 2-OH Ar—CHO —OCOCH₃ 22 diAcAC 10.25 2.33, 2.32 34, 36 AcAC 12.53 10.28 2.35 43 AcMAC 10.22 2.33 45 diAcAF 10.24 2.34, 2.33 unit: ppm

No. Schiff base-1 Ar—CH═N— —CH₂CO— —CO₂CH₃  6 AC GlyOMe 8.59 4.35 3.77 10 MAC GlyOMe 8.67 4.38 3.77 18 AS-6 GlyOMe 8.58 4.35 3.76 26 AcAC GlyOMe 8.69 4.40 3.77, 2.33 unit: ppm

No. Schiff base-2 Ar—CH═N— —CH₂CO— —OCOCH₃ 11 MAC GlyNH₂ 8.71 4.33 13 AC GlyNH₂ 8.63 4.30 15 AF GlyNH₂ 8.62 4.29 17 AS-6 GlyNH₂ 8.69 4.32 23 AcAC GlyNH₂ 8.73 4.34 2.35 unit: ppm

No. Schiff base-3 Ar—CH═N— —CH(NHAc)CO₂H ═N—CH₂— —NHCOCH₃ 14 MAC NAcLysOH 8.47 4.30 3.46 2.35 16 AC NAcLysOH 8.29 4.27 3.45 2.31 19 AS-6 NAcLysOH 8.48 4.30 3.47 2.35 unit: ppm

No. Schiff base-4 Ar—CH═N— ═NCH₂CH₂— —CH₂CONH₂ —OCOCH₃ 25 MAC âAlaNH₂ 8.69 3.89 2.60 27, 37 AcAC âAlaNH₂ 8.71 3.91 2.61 2.33 30 AS-6 âAlaNH₂ 8.67 3.89 2.62 31 AC âAlaNH₂ 8.60 3.87 2.61 unit: ppm

No. Schiff base-5 Ar—CH═N— PhH —CH(Bn)CONH₂ —OCOCH₃ 39 AcAC PheNH₂ 8.63 7.31 4.12 2.33 40 MAC PheNH₂ 8.63 7.31 4.10 41 AC PheNH₂ 8.43 4.09 unit: ppm

No. Schiff base-6 Ar—CH═N— —CH(Me)CONH₂ —CH(CH₃)CONH₂ —OCOCH₃ 42 MAC AlaNH₂ 8.72 4.04 1.58 44 AcAC AlaNH₂ 8.74 4.04 1.58 2.34 48 AcAF AlaNH₂ 8.74 4.04 1.59 2.34 unit: ppm

No. Acetal-1 of AC 2-OH —CH(OMe)₂ —CH(OCH₃)₂ —OCOCH₃ 32 diMe AcAC 9.21 5.65 3.41 2.32 unit: ppm

No. Acetal-2 of AC 2-OH —CH(OEt)₂ —CH(OCH₂CH₃)₂ —OCOCH₃ —CH(OCH₂CH₃)₂ 35 diEt AcAC 9.44 5.76 3.54 2.31 1.24 46 diEt MAC 9.32 5.76 3.65 1.24 47 diEt AcAF 9.40 5.76 3.64 2.31 1.24 unit: ppm

No. Acetal-3 of AC 2-OH —CH(OBu)₂ —CH(OCH₂—Pr)₂ —CH(OC₃H₆—CH₃)₂ 49 diBu MAC 9.31 5.74 3.57 0.89 unit: ppm

No. Acetal-4 of AC 2-OH —CH(—OC₃H₆O—) —CH(—OCH₂CH₂CH₂O—) 50 PG MAC 8.82 5.81 4.30, 3.98 unit: ppm

-   8. List of Structural Formulae of Ascochlorin Derivatives

The structural formulae of the ascochlorin derivatives are shown below, which are determined on the basis of the production described in 1 to 4 above and the data obtained in 5 to 7 above.

No. Abbreviation R₁ ═N—R₂ R₃ R₄ 5,7 AC + LysOH

—H —H 6,8 AC + GlyOMe

—H —H  9 AC + GlyOH

—H —H 10 MAC + GlyOMe

—Me —H 11 MAC + GlyNH₂

—Me —H 12 MAC + GlyOH

—Me —H 13 AC + GlyNH₂

—H —H 14 MAC + NAcLysOH

—Me —H 15 AF + GlyNH₂

—H —H 16 AC + NAcLysOH

—H —H 17 AS-6 + GlyNH₂

—CH₂CO₂H —H 18 AS-6 + GlyOMe

—CH₂CO₂H —H 19 AS-6 + NAcLysOH

—CH₂CO₂H —H 20 MAC + LysOH

—Me —H 22 diAcAC

═O —Ac —Ac 23 AcAC + GlyNH₂

—Ac —H 25 MAC + âAlaNH₂

—Me —H 26 AcAC + GlyOMe

—Ac —H 27 AcAC + âAlaNH₂

—Ac —H 28 MAC + Orn

—Me —H 30 AS-6 + âAlaNH₂

—CH₂CO₂H —H 31 AC + âAlaNH₂

—H —H 32 diMeAcAC

—OMe,—OMe —Ac —H 34 AcAC

═O —Ac —H 35 diEtAcAC

—OEt,—OEt —Ac —H 36,37 AcAC

═O —Ac —H 37 AcAC + âAlaNH₂

—Ac —H 39 AcAC + PheNH₂

—Ac —H 40 MAC + PheNH₂

—Me —H 41 AC + PheNH₂

—H —H 42 MAC + AlaNH₂

—Me —H 43 AcMAC

═O —Me —H 44 AcAC + AlaNH₂

—Ac —H 45 diAcAF

═O —Ac —Ac 46 diEtMAC

—OEt,—OEt —Me —H 47 diEtAcAF

—OEt,—OEt —Ac —H 48 AcAF + AlaNH₂

—Ac —H 49 diBuMAC

—OBu,—OBu —Me —H 50 PGMAC

—OCH₂CH₂CH₂O— —Me —H

The method of the present invention is very useful in synthesizing novel ligands which activate nuclear receptors. This is because such ligands have the function of regulating the expression of gene information involved in the onset and exacerbation of lifestyle-related diseases, chronic inflammation and malignant tumors, etc. In particular, ascochlorin and cylindrochlorin are extremely useful as resources for new pharmaceuticals because they can serve as mother compounds for synthesis of novel nuclear receptor ligands when their hydroxyl groups at the 2- and 4-positions are modified with alkyl or acyl groups.

The compound of the present invention may be administered by any route of administration permitted for other drugs available for similar applications and in the form of a pure preparation or an appropriately formulated pharmaceutical composition. Thus, the administration can be accomplished, for example, in the dosage form of solid, semi-solid, lyophilized powder or liquid (e.g., tablets, suppositories, pills, capsules, powders, solutions, suspensions, emulsions, creams, lotions, aerosols, ointments, gels) by oral, intranasal, parenteral or topical route, preferably in an appropriate unit dose form which allows an exact volumetric dosing in one administration. Such a composition is composed of commonly used pharmaceutical carriers or excipients and the compound of the present invention and may also be supplemented with other medical pharmaceuticals and/or various pharmaceutically acceptable additives such as carriers and absorption aids. In general, such a composition acceptable as a formulation may comprise about 1% to 99% by weight of the compound of the present invention and about 99% to 1% by weight of appropriate pharmaceutical additives, depending on the dosage form to be administered. In this composition, the compound of the present invention as a medical pharmaceutical constitutes about 5% to 75% of the composition and the balance comprises appropriate pharmaceutical excipients. The effective daily dose required for the compound of the present invention to ameliorate a pathological condition is 0.1 to 20 mg/kg, desirably 0.2 to 5 mg/kg of body weight for adults.

Dosage forms preferred for the diseases explained in detail above may be achieved by formulating in such a manner as to select a dosage set to be adjustable depending on the severity of the diseases. In formulating, most important is the limitation arising from the fact that the compound of the present invention is fat-soluble. Since ligands for the nuclear receptor superfamily are fat-soluble hormones or vitamins, it is therefore natural to believe that the compound of the present invention is also fat-soluble. Pharmaceutically acceptable additives for use in oral administration may be adjusted by adding any excipient commonly available, including mannite, lactose, starch, magnesium stearate, saccharin sodium, talc, cellulose, glucose, gelatin, sucrose or magnesium carbonate. Such a composition may be in the form of a solution, tablet, pill, capsule, powder or sustained-release formulation, etc.

The composition is preferably in the form of a tablet or a pill, which comprises the compound of the present invention together with a diluent (e.g., lactose, sucrose, dicalcium phosphate), a disintegrating agent (e.g., starch and derivatives thereof), a lubricant (e.g., magnesium stearate), and a binder (e.g., starch, gum arabic, polyvinylpyrrolidone, gelatin, cellulose and derivatives thereof), as well as a surfactant having the ability to water the particle surface of the compound of the present invention which is highly fat-soluble and water-repellent, a fat-soluble additive, bile acid, a phospholipid, etc. It is particularly preferable to comprise an aliphatic synthetic surfactant or an organic solvent-soluble polymeric aid. Examples of these materials include gum arabic, sodium alginate, methylcellulose, carboxymethyl cellulose, hydroxypropylcellulose, polyvinylpyrrolidone, bentonite, sodium lauryl sulfate, Polysorbate 80, sorbitan monofatty acid ester, and polyoxyl 40 stearate.

EXAMPLES

The present invention will now be further illustrated by way of the following examples, which are not intended to limit the scope of the invention.

Example 1 Synthesis of Imino Compounds Starting with Ascochlorin Derivatives

Ascochlorin and its derivatives (Compounds-1 & -2, ascofuranone) were condensed with amino acid derivatives having a primary amine in the presence or absence of a base (e.g., triethylamine, potassium carbonate) and in a solvent (e.g., methanol, tetrahydrofuran (THF)).

After confirming the progress of the reaction (i.e., the formation of imino compounds appearing as band yellow spots) by thin-layer chromatography (TLC), the Schiff bases were extracted from the reaction solutions and then evaporated to remove the solvent under reduced pressure, or alternatively, the reaction solvent was directly distilled off under reduced pressure. In this way, concentrates containing imino compounds were obtained.

The concentrates were purified by silica gel column chromatography to isolate the imino compounds.

Other things to be noted are as shown below.

-   (1) The yield was varied over a wide range from 10% up to a     quantitative level depending on the reactivity. -   (2) Each product was an imino compound formed by reaction with the     aldehyde group of each starting compound. -   (3) Compound-1 and Compound-2 having a protected hydroxyl group at     the 4-position are highly reactive. -   (4) Glycine amide formed an imino compound with each of the     ascochlorin and derivatives thereof.

The results obtained are shown in Tables 4 to 8 below.

TABLE 4 List of compounds along with their yields Amino compound Glycine Starting methyl Glycine N-Acetyl material Glycine ester amide lysine Lysine AC  9 (trace) 6&7 (55%) 13 (80%) 16 (10%) 5&7 (<10%) Com- 12 (trace)  10 (81%) 11 (81%) 14 (80%)  20 (<10%) pound-1 Com- 17 (94%) 19 (10%) pound-2 AF 15 (23%) Numbers in parentheses: Yields calculated from starting materials Abbreviations: GlyOH = glycine, GlyOMe = glycine methyl ester, GlyNH₂ = glycine amide, NacLysOH = α-N-acetyl lysine, LysOH = lysine AC = ascochlorin, Compound-1 = 4-O-methylascochlorin, Compound-2 = 4-O-carboxymethylascochlorin, AF = ascofuranone

TABLE 5 Thin-layer chromatography: Confirmation of Rf value and purity Rf No. Imino compound Developing solvent value TLC purity 6, 8 AC GlyOMe 50% AcOEt/Hexane 0.33 One spot 10 MAC GlyOMe 50% AcOEt/Hexane 0.36 One spot 11 MAC GlyNH₂  5% MeOH/CHCl₃ 0.53 Slightly impure 13 AC GlyNH₂  5% MeOH/CHCl₃ 0.57 One spot 14 MAC NAcLysOH 20% MeOH/CHCl₃ 0.04 Decomposed 15 AF GlyNH₂ 10% MeOH/CHCl₃ 0.54 One spot 16 AC NAcLysOH 20% MeOH/CHCl₃ 0.27 One spot 17 AS-6 GlyNH₂ 20% MeOH/CHCl₃ 0.41 One spot (containing Et₃N) 18 AS-6 GlyOMe 20% MeOH/CHCl₃ 0.57 One spot Note) Et₃N: triethylamine Abbreviations: GlyOH = glycine, GlyOMe = glycine methyl ester, GlyNH₂ = glycine amide, NacLysOH = α-N-acetyl lysine, LysOH = lysine AC = ascochlorin, Compound-1 = 4-O-methylascochlorin, Compound-2 = 4-O-carboxymethylascochlorin, AF = ascofuranone

TABLE 6 Infrared absorption (cm⁻¹) for carbonyl region No. AC compound Carbonyl region cm⁻¹ (?: visual judgment) AC 1704 1629 Compound-1 1715 1641 Compound-2 1738 1712 1638 AF 1739 1633 No. Imino compound Ketone region cm⁻¹ (?: visual judgment) AC 1704 1629 6, 8 AC GlyOMe 1739 1709 1621 ?1602 13 AC GlyNH₂ 1698 1666  1602 16 AC NAcLysOH 1704 1634 ?1601 Compound-1 1715 1641 10 ″ GlyOMe 1749 1710 1625 ?1598 11 ″ GlyNH₂ 1702 1620 14 ″ NAcLysOH 1704 1633 Compound-2 1738 1712 1638 17 ″ GlyNH₂ 1702 1618 18 ″ GlyOMe 1748 1708 1622 ?1600 AF 1739 1633 15 AF GlyNH₂ 1750 1682 1645  1600 Abbreviations: GlyOH = glycine, GlyOMe = glycine methyl ester, GlyNH₂ = glycine amide, NacLysOH = α-N-acetyl lysine, LysOH = lysine AC = ascochlorin, Compound-1 = 4-O-methylascochlorin, Compound-2 = 4-O-carboxymethylascochlorin, AF = ascofuranone

TABLE 7 Nuclear magnetic resonance spectrum-1 (NMR) AC compound & No. imino compound Chemical shift (excerpt) ppm AC 10.1(Ar—CHO)  6, 8 AC GlyOMe 8.6(—N═CH—Ar), 4.3(—CH₂CO—), 3.8(—CO₂Me) 13 AC GlyNH₂ 8.6(—N═CH—Ar), 4.3(—CH₂CO—) 16 AC NAcLysOH Structure not yet determined by NMR Com- 10.2(Ar—CHO) pound-1 10 MAC GlyOMe 8.6(—N═CH—Ar), 4.3(—CH₂CO—), 3.8(—CO₂Me) 11 MAC GlyNH₂ 8.7(—N═CH—Ar), 4.3(—CH₂CO—) 14 MAC NAcLysOH Structure not yet determined by NMR Com- 10.3(Ar—CHO) pound-2 17 AS-6 GlyNH₂ 8.7(—N═CH—Ar), 4.3(—CH₂CO—) 18 AS-6 GlyOMe 8.6(—N═CH—Ar), 4.3(—CH₂CO—), 3.8(—CO₂Me) AF 10.1(Ar—CHO) 15 AF GlyNH₂ 8.6(—N═CH—Ar), 4.3(—CH₂CO—) Abbreviations: GlyOH = glycine, GlyOMe = glycine methyl ester, GlyNH₂ = glycine amide, NacLysOH = α-N-acetyl lysine, LysOH = lysine AC = ascochlorin, Compound-1 = 4-O-methylascochlorin, Compound-2 = 4-O-carboxymethylascochlorin, AF = ascofuranone

TABLE 8 Nuclear magnetic resonance spectrum-2 (NMR) AC compound & No. imino compound Chemical shift (excerpt) ppm AC 10.1(Ar—CHO)  6, 8 AC GlyOMe 8.6(—N═CH—Ar), 4.3(—CH₂CO—), 3.8(—CO₂Me) 13 AC GlyNH₂ 8.6(—N═CH—Ar), 4.3(—CH₂CO—) 16 AC NAcLysOH Structure not determined by NMR Com- 10.2(Ar—CHO) pound-1 10 ″ GlyOMe 8.6(—N═CH—Ar), 4.3(—CH₂CO—), 3.8(—CO₂Me) 11 ″ GlyNH₂ 8.7(—N═CH—Ar), 4.3(—CH₂CO—) 14 ″ Structure not determined by NMR Com- 10.3(Ar—CHO) pound-2 17 ″ GlyNH₂ 8.7(—N═CH—Ar), 4.3(—CH₂CO—) 18 ″ GlyOMe 8.6(—N═CH—Ar), 4.3(—CH₂CO—), 3.8(—CO₂Me) AF 10.1(Ar—CHO) 15 AF GlyNH₂ 8.6(—N═CH—Ar), 4.3(—CH₂CO—)

The structures of the synthesized compounds are shown below. Abbreviations in figure: MAC=Compound-1, AS-6=Compound-2

Example 2

Ascochlorin (405 mg, 1 mM) was dissolved in 10 ml tetrahydrofuran and a solution of glycine amide (85 mg, 1.15 mM) in 5% triethylamine-containing methanol (5 ml) was slowly added thereto while stirring at room temperature. After completion of the addition, stirring was continued at room temperature and the reaction was monitored by silica gel thin-layer chromatography. The developing solvent used was methanol:chloroform=5:95. After 16 hours, the spot corresponding to ascochlorin was found to disappear and there was only a yellow spot indicative of a Schiff base between ascochlorin and glycine amide (Rf: 0.57); the reaction solution was concentrated to dryness under reduced pressure. The dried yellow amorphous powder was dissolved in a small amount of methanol and separated by silica gel column chromatography (solvent: 10% methanol-containing dichloromethane) into the Schiff base and impurities. The yellow eluates containing only the Schiff base were collected and evaporated to dryness under reduced pressure to give the Schiff base formed between the aldehyde group of ascochlorin and an amino group of glycine amide (367 mg, yield 80%).

Infrared absorption band (cm⁻¹): 3420, 2974, 1698, 1666, 1606, 1419, 1252, 1112, 969

Nuclear magnetic resonance spectrum: The structure was determined by disappearance of the aldehyde proton of ascochlorin, appearance of an azomethine proton, and appearance of protons belonging to the methylene group of glycine amide. The chemical shifts of protons attached to these groups are as follows: Ar—CH═N—; 8.63, —CH ₂CONH₂; 4.38 (unit: ppm), where Ar in Ar—CH═N— represents a molecule formed by removing aldehyde from ascochlorin, and —C═ in —C═N— represents the aldehyde carbon of ascochlorin attached to an amino group of glycine amide.

Elemental Analysis

(Calculated for C₂₅H₃₃O₄N₂Cl): C, 65.15; H, 7.17; N, 6.08, Cl 7.71. (Found): C, 65.08; H, 7.20; N, 6.05, Cl 7.82.

Example 3

Diacetylascochlorin (490 mg, about 1 mM) and β-alanine amide (176 mg, 2 mM) were dissolved in 50 ml tetrahydrofuran and boiled under reflux for 1 hour. After 1 hour, when examining by silica gel thin-layer chromatography (developing solvent: 10% methanol-containing chloroform), the spot corresponding to acetylascochlorin was found to disappear and there was only a yellow spot indicative of a Schiff base between acetylascochlorin and β-alanine amide; the reaction solution was rapidly cooled to room temperature and concentrated to dryness under reduced pressure. The product obtained was a yellow amorphous powder. This yellow powder was dissolved in a small amount of methanol and applied to silica gel column chromatography as in the case of Example 1 to give the Schiff base (molecular formula: C₂₈H₃₇O₄N₂Cl, molecular weight: 516.5) formed between the aldehyde group of acetylascochlorin and an amino group of β-alanine amide as a yellow amorphous powder (507 mg, yield 98%).

Infrared absorption band (cm⁻¹): 3425, 2972, 1776, 1674, 1628, 1423, 1371, 1200, 1095

Nuclear magnetic resonance spectrum: The structure was determined by disappearance of the aldehyde proton of ascochlorin, appearance of an azomethine proton, and appearance of protons belonging to the methylene groups of glycine amide. The chemical shifts of protons attached to these groups are as follows: Ar—CH═N—; 8.71, ═N—CH ₂—CH₂CONH₂; 3.91, ═N—CH₂—CH ₂CONH₂; 2.61, —O—COCH ₃; 2.33 (unit: ppm), where Ar in Ar—CH═N— represents a molecule formed by removing aldehyde from ascochlorin, and —C═ in —C═N— represents the aldehyde carbon of ascochlorin attached to an amino group of β-alanine amide.

Elemental Analysis

(Calculated for C₂₈H₃₇O₅N₂Cl): C, 65.05; H, 7.16; N, 6.08, Cl 5.42. (Found): C, 64.98; H, 7.22; N, 6.05, Cl 5.72.

Example 4

4-O-Methylascochlorin (420 mg, about 1 mM) and L-phenylalanine amide (200 mg, 1.22 mM) were dissolved by heating in 20 ml tetrahydrofuran. After dissolution, 30 mg of triethylamine was added to start the reaction while stirring at room temperature. The reaction was monitored by silica gel thin-layer chromatography using a 1:9 mixture of methanol and chloroform as a developing solvent. After 16 hours, the spot corresponding to 4-O-methylascochlorin was found to disappear and there was only a yellow spot indicative of a Schiff base (Rf: 0.36); the reaction solution was concentrated to dryness under reduced pressure. The resulting yellow amorphous powder was dissolved in a small amount of methanol and applied to silica gel column chromatography (solvent: 10% methanol-containing dichloromethane) to purify the Schiff base. The yellow eluates containing only the Schiff base were collected and evaporated to dryness under reduced pressure to give the Schiff base formed between the aldehyde group of 4-O-methylascochlorin and an amino group of L-phenylalanine amide (423 mg, yield 75%).

Infrared absorption band (cm⁻¹): 3446, 2936, 1711, 1621, 1454, 1414, 1358, 1250, 1167, 1108, 1008, 970, 751, 698

Nuclear magnetic resonance spectrum: The structure was determined by disappearance of the aldehyde proton of ascochlorin, appearance of an azomethine proton, and appearance of protons belonging to the methine group and the phenylalanine aromatic ring of phenylalanine amide. The chemical shifts of protons attached to these groups are as follows: Ar—CH═N—; 8.63, PhH; 7.31, —CHCONH₂; 4.10 (unit: ppm), where Ar in Ar—CH═N— represents a molecule formed by removing aldehyde from ascochlorin, and —C═ in —C═N— represents the aldehyde carbon of ascochlorin attached to an amino group of glycine amide.

Elemental Analysis

(Calculated for C₃₃H₄₁O₄N₂Cl): C, 70.15; H, 7.26; N, 4.96, Cl 6.29. (Found): C, 70.28; H, 7.19; N, 5.05, Cl 6.33.

Example 5

4-O-Carboxymethylascochlorin (463 mg, about 1 mM) and α-N-acetyl-L-lysine (300 mg, about 1.6 mM) were dissolved by heating in 50 ml methanol and reacted while stirring at room temperature in the presence of finely powdered potassium carbonate (50 mg) as a catalyst. When the reaction was monitored by silica gel thin-layer chromatography, after 16 hours, the spot corresponding to the starting material 4-O-carboxymethylascochlorin was found to disappear and there was only a yellow spot of the reaction product. The reaction solution was immediately concentrated under reduced pressure to remove the solvent and the residue was evaporated to dryness in a vacuum desiccator. The resulting yellow amorphous powder was then dissolved in a small amount of methanol and applied to silica gel column chromatography (solvent: 20% methanol-containing dichloromethane) to purify the formed Schiff base. The yellow eluates containing only the Schiff base were collected and evaporated to dryness under reduced pressure to give the Schiff base formed between the aldehyde group of 4-O-carboxymethylascochlorin and the free amino group of α-N-acetyl-L-lysine (278 mg, yield 44%).

Nuclear magnetic resonance spectrum: The structure was determined by disappearance of the aldehyde proton of ascochlorin, appearance of an azomethine proton, and appearance of protons from α-N-acetyl-L-lysine (i.e., protons from methane, methylene adjacent to the nitrogen, and methyl of the α-N-acetyl group). The chemical shifts of protons attached to these groups are as follows: Ar—CH═N—; 8.48, —CH(NHCOCH₃)COOH; 4.30, ═N—CH₂—; 3.47, —NHCOCH₃; 2.35 (unit: ppm).

Elemental Analysis

(Calculated for C₃₃H₄₅O₈N₂Cl): C, 62.61; H, 7.11; N, 4.43, Cl 5.61. (Found): C, 62.88; H, 7.14; N, 4.37, Cl 5.80.

Example 6 Effect on Genetically Obese Diabetic Mice C57BL/ksj db/db(db/db Mice)

A solution of Compound-16 (1 g) in acetone (about 50 ml) was sprinkled over and mixed well with 1 kg of rodent standard feed (CE-2, CLEA Japan, Inc., Japan), followed by air-drying in a chamber. The content of Compound-16 in this feed was about 0.1%. In the same manner, pellet chow samples containing 0.05% to 0.025% of Compound-16 were prepared and used for the experiment. To prepare control feed, the same powder feed was sprinkled with acetone and palletized. Twenty male db/db mice (8 weeks of age after birth) were randomly divided into 4 groups. Each group was housed in a cage for urine collection and fed with the Compound-16-containing feed or the control feed for 21 days. During the housing, the mice were allowed to take feed and water ad libitum and their urine was collected at the intervals indicated in Table 1 to determine urinary sugar excretion by an enzymatic method. The level of urinary sugar excretion was expressed as the mean per animal.

TABLE 9 Effect of Compound-16 to reduce urinary sugar excretion Level of urinary sugar excretion (mg/mouse/day) (%) 0 days¹⁾ 1 day 3 days 7 days 14 days 21 days 0.1 814 187 30 15 10 10 0.05 786 541 231 253 170 52 0.025 890 600 452 175 201 134 Control group 721 802 760 777 860 858 ¹⁾Urine was collected for 24 hours beginning 1 day before initiation of the experiment.

Example 7 Effect of Lowering Serum Cholesterol in Normal Mice

Fifty ICR male mice (5 weeks of age) were randomly divided into 5 groups of 10 animals each and housed in polycarbonate cages at 5 animals per cage. One group for use as a control group was fed with standard feed powder for mice alone, while the other 4 groups were fed for 1 week with the same feed powder supplemented with 0.05% of 4 powdered ascochlorin carboxylic acid derivatives, respectively. With respect to body weight gain during the experiment, each group showed no statistically significant difference over the control group, and there was no effect induced by drug administration. After 1 week, the blood was collected from the heart of each mouse to determine the level of serum total cholesterol by an enzymatic method.

TABLE 10 Effect of ascochlorin derivatives to lower serum cholesterol Compound name Serum total cholesterol (added at 0.1%) (mg/dl) Remarks Control group 143   Compound-8  93*** Not toxic Compound-13 112**  ″ Compound-10 125*  ″ Compound-19  95**  ″ Student's t-test: *P < 0.05, **P < 0.01 and ***P < 0.001

As shown in FIGS. 1 and 2, prenylphenol is attached to the ω-amino group of a feed protein lysine residue through aminocarbonyl reaction to form a Schiff base. When taken by animals, the Schiff base will be hydrolyzed in the small intestine by the action of protease to generate an imino compound in which prenylphenol is attached to the ω-amino group of lysine. Since this imino compound is easily dissolved in water, it will be readily absorbed from the small intestine and cause an exchange reaction with serum albumin in the blood, so that prenylphenol is transferred to a lysine residue ω-amino group of serum albumin. Serum albumin having prenylphenol attached to its ω-amino group will be taken up by target organ cells, where the albumin will be degraded to regenerate prenylphenol. Namely, prenylphenol covalently attached to feed protein will be absorbed, delivered through the blood and reach target cells with its toxicity being masked, thereby exerting its efficacy without showing strong toxicity.

INDUSTRIAL APPLICABILITY

The imino compound (Schiff base) of the present invention is useful in treating and/or preventing diabetes, in treating arteriosclerosis, in lowering serum cholesterol, in treating multiple risk factor syndrome, in treating hypertension, in treating myxedema, in treating chronic inflammation, and in preventing and/or treating restenosis of arterial lumen dilated with a balloon catheter or stent, etc. Moreover, it is also useful as a survival promoter for ensuring survival of cells or tissues differentiated and induced from stem cells to be transplanted to a recipient in regenerative medicine. Further, the imino compound of the present invention is a compound belonging to the third generation shown in FIG. 2 and hence shows a significant effect on the duration of efficacy.

In view of the foregoing, the compound of the present invention is extremely promising as a pharmaceutical preparation because it is effective for various diseases and has a longer duration. 

1. A compound of the following formula or a pharmaceutically acceptable salt of the compound or optical isomers thereof:

(wherein R₁ represents one of the following two groups:

R₂ represents —(CH₂)_(n)—CHR₅R₆ (wherein R₅ represents a hydrogen atom, an amino group, an amino group substituted with one or two C₁₋₆ alkyl groups, or a C₁₋₆ alkyl group substituted with phenyl, R₆ represents a carboxyl group, —CONH₂, or —COOR₇ (wherein R₇ represents a substituted or unsubstituted C₁₋₆ alkyl group), and n represents 0 or an integer of 1 to 6) or a residue formed by removing NH₂ ftom any amino acid, R₃ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group, and R₄ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group).
 2. The compound according to claim 1, wherein R₄ is a substituted or unsubstituted C₁₋₆ alkyl group, or a pharmaceutically acceptable salt of the compound or optical isomers thereof.
 3. The compound according to claim 1, wherein R₄ is an acyl group, or a pharmaceutically acceptable salt of the compound or optical isomers thereof.
 4. The compound according to claim 1, wherein R₃ is a substituted or unsubstituted C₁₋₆ alkyl group, or a pharmaceutically acceptable salt of the compound or optical isomers thereof.
 5. The compound according to claim 1, wherein R₃ and R₄, which may be the same or different, are each a substituted or unsubstituted C₁₋₆ alkyl group, or a pharmaceutically acceptable salt of the compound or optical isomers thereof.
 6. The compound according to claim 1, wherein R₃ is a substituted or unsubstituted C₁₋₆ alkyl group and R₄ is an acyl group, or a pharmaceutically acceptable salt of the compound or optical isomers thereof.
 7. The compound according to claim 1, wherein R₃ is an acyl group and R₄ is a substituted or unsubstituted C₁₋₆ alkyl group, or a pharmaceutically acceptable salt of the compound or optical isomers thereof.
 8. A pharmaceutical composition which comprises one or more members of a compound of the following formula or a pharmaceutically acceptable salt of the compound or optical isomers thereof, as well as a pharmaceutically acceptable additive including a carrier and a diluent:

(wherein R₁ represents one of the following two groups:

R₂ represents —(CH₂)_(n)—CHR₅R₆ (wherein R₅ represents a hydrogen atom, an amino group, an amino group substituted with one or two C₁₋₆ alkyl groups, or a C₁₋₆ alkyl group substituted with phenyl, R₆ represents a carboxyl group, —CONH₂, or —COOR₇ (wherein R₇ represents a substituted or unsubstituted C₁₋₆ alkyl group), and n represents 0 or an integer of 1 to 6) or a residue formed by removing NH₂ from any amino acid, R₃ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group, and R₄ represents a hydrogen atom, a substituted or unsubstituted C₁₋₆ alkyl group, a substituted or unsubstituted C₂₋₆ alkenyl group, a substituted or unsubstituted C₂₋₆ alkynyl group, a substituted or unsubstituted C₃₋₈ cycloalkyl group, an acyl group, an aryl group or a carboxyl group).
 9. A method for treating diabetes, which comprises administering to a patient a therapeutically effective amount of one or more members of the compound according to claim 1 or a pharmaceutically acceptable salt of the compound or optical isomers thereof.
 10. A method for treating arteriosclerosis, which comprises administering to a patient a therapeutically effective amount of one or more members of the compound according to claim 1 or a pharmaceutically acceptable salt of the compound or optical isomers thereof.
 11. A method for lowering serum cholesterol, which comprises administering to a patient a therapeutically effective amount of one or more members of the compound according to claim 1 or a pharmaceutically acceptable salt of the compound or optical isomers thereof.
 12. The compound according to claim 1, wherein R₂ is a residue formed by removing NH₂ from glycine, N-acetyllysine or β-alanine, R₃ is a hydrogen atom, a methyl group or a carboxymethyl group, and R₄ is a hydrogen atom, or a pharmaceutically acceptable salt of the compound or optical isomers thereof.
 13. A Schiff base of claim 1 which is 3-[5-[1(R),2(S),6(S)-trimethyl-3-oxocyclohexyl]-3-methyl-2,4-pentadienyl]-2-hydroxyl-4-methoxy-5-chloro-6-methylbenzaldehyde and glycinamide (Compound No. 11).
 14. A Schiff base of claim 1, which is 3-[5-[1(R),2(S),6(S)-trimethyl-3-oxocyclohexyl]-3-methyl-2,4-pentadienyl]-2-hydroxyl-4-methoxy-5-chloro-6-methylbenzaldehyde and N-acetyllysine (Compound No. 14).
 15. A Schiff base of claim 1, which is 3-[5-[1(R),2(S),6(S)-trimethyl-3-oxocyclohexyl]-3-methyl-2,4-pentadienyl]-2-hydroxyl-4-carboxymethoxy-5-chloro-6-methylbenzaldehyde and N-acetyllysine (Compound No. 19).
 16. A Schiff base of claim 1, which is 3-[5-[1(R),2(S),6(S)-trimethyl-3-oxocyclohexyl]-3-methyl-2,4-pentadienyl]-2-hydroxyl-4-carboxymethoxy-5-chloro-6-methylbenzaldehyde and β-alanine (Compound No. 30). 